OFFSET
0,3
COMMENTS
a(n)=a(3n)=a(3n+2)/3; a(3n+2)=0.
LINKS
Antti Karttunen, Table of n, a(n) for n = 0..19683
FORMULA
a(n)=sum{k=0..n, L(C(n,k)/3)*(-1)^k} where L(j/p) is the Legendre symbol of j and p.
PROG
(PARI) A117980(n) = sum(k=0, n, kronecker(binomial(n, k), 3)*((-1)^k)); \\ Antti Karttunen, Sep 20 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Apr 06 2006
STATUS
approved